Powershift transmission for agricultural machines

ABSTRACT

A powershift transmission for an agricultural machine includes a transmission housing, an input shaft unit and an output shaft, wherein the input shaft unit and the output shaft extend at least at a distance within the transmission housing. An auxiliary shaft is arranged within the housing parallel to but offset between the input shaft unit and the output shaft. The input shaft unit and the auxiliary shaft are connected to one another via a front-mounted range unit, and the auxiliary shaft and the output shaft are connected to one another via a rear-mounted range unit. The front-mounted and rear mounted range units each includes at least two gear wheel pairs. The input shaft unit is formed from a main input shaft and an auxiliary input shaft.

RELATED APPLICATIONS

This application claims priority to European Patent Application Ser. No. 19161101.1, filed Mar. 6, 2019, European Patent Application Ser. No. 19161089.8, filed Mar. 6, 2019, European Patent Application Ser. No. 19161083.1, filed Mar. 6, 2019, and European Patent Application Ser. No. 19161074.0, filed Mar. 6, 2019, the disclosures of which are hereby incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a powershift transmission for agricultural machines.

BACKGROUND

Powershift transmissions are a special form of vehicle transmissions in which the transmission ratio can be changed under load, that is to say during travel, without interrupting the torque. As a result, propulsion forces can be transmitted even during the shifting operation so the vehicle can continue to accelerate even during the shifting operation. Therefore, no decreases in comfort occur during the shifting operation. In agricultural utility vehicles, particularly in tractors, powershift transmissions are mainly used because they permit faster work, in particular when working on hilly terrain and on changing types of soil, and help to save fuel. Some tractor transmissions can also only be partially power shifted, which means that shifting without an interruption in the tractive force can only be performed between some of the gears, while other gears (for example, a group change) are associated with an interruption in the tractive force.

It is known to form such transmissions in conjunction with planetary gear mechanisms and clutches in a modular system, so that by virtue of a corresponding design and arrangement of gear wheel pairs of the planetary gear mechanism, the powershift transmission can be operated in various operating modes, such as a through-connected drive mode, gear reduction mode and reversing mode. Therefore, on tractors powershift transmissions are used as a pre-stage transmission which, depending on the design of a multi-step planetary set, can either be operated in the through-connected drive mode or reversing mode operating modes or in the through-connected drive mode or gear reduction mode operating modes.

These transmissions are characterized by the fact that in a first shift operation a clutch which is connected to an input shaft connects the input shaft to the output shaft, so that the transmission can be operated in the through-connected drive mode, wherein the planetary gear mechanism turns freely. In a second shift operation, the clutch is released so that the planetary carrier is driven by the input shaft and the planetary set revolves around a first sun gear which is fixed in place by a brake through which the output shaft extends. The power output occurs via a second sun gear which is connected to the output shaft and is driven by the planetary set. Depending on the assignment of the planetary set and the design of the gear sets of planetary set and sun gears, the powershift transmission may be operated in gear reduction mode or in reversing mode.

Therefore, a two-stage powershift transmission is made available which is, however, on the one hand costly in terms of fabrication technology and, on the other hand, does not permit a further operating mode, for example, a crawling speed mode, in the specified arrangement.

EP 0 745 198 B1 describes a powershift transmission for mobile working machines and a method for controlling this powershift transmission. In this context, hydraulic motors are used which are connected to one another via a clutch. In a lower speed range, the hydraulic motors are connected together in a torque-adding fashion. One of the hydraulic motors is reconfigured by a further clutch so that the hydraulic motors can be operated in an adding fashion in an upper speed range rotational speed.

WO 2013/064371 A1 describes a powershift transmission with an input shaft and an output shaft which is arranged coaxially with respect thereto. The powershift transmission has a planetary gear set. The planetary gear set comprises a planet carrier which is connected to the input shaft. The first output shaft can be connected to the output-side sun of a multi-step planetary set by a shift element. The first output shaft can be connected directly to the input shaft by a second shift element. The input-side sun gear of the multi-step planetary set is connected in a rotationally fixed fashion to a housing part of the powershift transmission.

Taking this prior art as a starting point, there is a need for a powershift transmission which can be embodied on the one hand with a high number of gear variants with a simultaneously compact size, and which, on the other hand, can be used for a wide application range.

SUMMARY

In the present disclosure, a powershift transmission has a transmission housing, an input shaft unit and an output shaft, wherein the input shaft unit and the output shaft extend within the transmission housing at least in certain sections, wherein an auxiliary shaft is arranged with a parallel offset between the input shaft unit and the output shaft within the housing, wherein the input shaft unit and the auxiliary shaft are connected to one another via a front-mounted range unit, and the auxiliary shaft and the output shaft are connected to one another via a rear-mounted range unit, wherein each range unit has at least two individual gear wheel pairs which can be coupled or decoupled, and wherein the input shaft unit is formed from a main input shaft and an auxiliary input shaft which can be coupled to one another via a reduction gear unit.

Within the scope of this disclosure, the terms coupling and decoupling of the individual gear wheel pairs mean that the gear wheel pairs are either in engagement with one another and then a torque can be transmitted from the one gear wheel to the other gear wheel of the gear wheel pair or that these gear wheels of a gear wheel pair are not in engagement with one another. When two gear wheels are in engagement with one another, the gear wheel pair is therefore a coupled one.

The powershift transmission can be coupled to a drive unit via the input shaft unit. The drive unit can be a drive machine such as, for example, an internal combustion engine. The drive unit is connected here to the powershift transmission via the main input shaft so that as a result the torque which is fed in can be transmitted to the output shaft via the powershift transmission. A working machine or a drive shaft, for example, for wheels can then be connected to the output shaft.

Overall, the powershift transmission has two range units and a reduction gear unit. A reduction gear unit is an extension of the manual transmission. The latter is usually composed of two reduction-gear-unit gear wheel pairs. These reduction-gear-unit gear wheel pairs can be connected to one another in a variety of ways and implement either a gear reduction or a transmission, at least in a shifted state. Finally, with the reduction gear unit it is thus possible to implement two shifted states, wherein one shifted state is provided for a low load state, and another shifted state is provided for a high load state. For this reason, the shifted states of the reduction gear unit are generally denoted by Hi (high) for the high load state and by Lo (low) for the low load state.

A multiplicity of individual gearshift variants can be implemented by means of the reduction gear unit and the front-mounted range unit and the rear-mounted range unit, each with at least two gear wheel pairs and correspondingly at least two shifted states. The reduction gear unit permits in this context the transmission of a torque between the main input shaft and the auxiliary input shaft, the front-mounted range unit permits transmission of the torque between the auxiliary input shaft and the auxiliary shaft, and the rear-mounted range unit permits a transmission of torque between the auxiliary shaft and the output shaft.

Accordingly, the maximum number of gearshift variants results from a multiplication of the number of gear wheel pairs of the front-mounted range unit, the number of gear wheel pairs of the rear-mounted range unit and the number of shifted states of the reduction gear unit. When there are at least two gear wheel pairs in the front-mounted range unit and in the rear-mounted range unit and two shifted states in the reduction gear unit a maximum number of eight gearshift variants thus results. However, this number can be increased in an easy way in that further gear wheel pairs are added in the front-mounted range unit or in the rear-mounted range unit.

An increase in a further gear wheel pair already gives rise to an additional four gearshift variants. Therefore, a multiplicity of different gearshift variants can be obtained by means of minor structural modifications so that the power transmission can be adapted individually depending on the application or the type of agricultural machine. However, for this purpose the transmission housing and also the shafts which are present can usually be retained, since according to one embodiment of the disclosure the additional engagement of gear wheel pairs does not require a change to this effect.

This is due, inter alia, to the fact that even with relatively few gear wheel pairs it is possible to obtain a large number of gearshift variants, and as result of this low number of gear wheel pairs only a small number of clutches have to be correspondingly provided. In the case of a powershift transmission, a separate clutch has to be provided for each gear wheel pair of the front-mounted range unit and of the rear-mounted range unit. Through the use of a reduction gear unit it is possible to reduce the number of clutches particularly in the case of high gearshift variants, wherein the reduction gear unit also requires at least two clutches.

In the case of an exemplary embodiment with 32 gearshift variants, both the front-mounted range unit and the rear-mounted range unit have four gear wheel pairs each. Accordingly, ten clutches are necessary to implement such a powershift transmission. As far as the reduction gear unit has been dispensed with, the same number of gearshift variants could be obtained, for example, by virtue of the fact that eight gear wheel pairs are provided for the front-mounted range unit and four gear wheel pairs are provided for the rear-mounted range unit. Therefore, a total of 12 clutches would be necessary. Therefore, in comparison, in the case of a powershift transmission according to the disclosure it is possible to dispense overall with two clutches. As a result it is possible for the overall size of the powershift transmission to be kept very compact. Moreover, within the transmission housing there is sufficient installation space available which permits the gear wheel pairs to be easily increased or reduced.

The gear wheel pairs each have a drive gear wheel and an output gear wheel, wherein the torque is transmitted from the drive gear wheel to the output gear wheel. In one embodiment, the drive gear wheels of the front-mounted range unit are arranged on the auxiliary input shaft, and the output gear wheels of the front-mounted range unit are arranged on the auxiliary shaft. Accordingly, the drive gear wheels of the rear-mounted range unit are arranged on the auxiliary shaft, and the output gear wheels of the rear-mounted range unit are arranged on the output shaft.

Owing to this front-mounted arrangement, the reduction gear unit generally only has relatively low step-up or step-down transmission ratios so that correspondingly small clutches have to be provided. The gear wheels of the reduction gear unit on the main input shaft and the auxiliary input shaft can be easily used to operate additional drive units. These drive units can be, for example, pumps, compressors or water pumps.

In this embodiment, a reversing unit may be integrated into the reduction gear unit. The purpose of this reversing unit is to reverse the direction of rotation of the shafts connected downstream of the reversing unit so that reversing is possible, for example, in the case of an agricultural machine. In such an embodiment, integrating this reversing unit into the reduction gear unit makes it possible to dispense with a load change. Instead of a reversing unit it is alternatively also possible to connect a so-called power reverser upstream.

Within the scope of the disclosure, in particular two alternatives have proven particularly advantageous for the embodiment of the reduction gear unit. Here, it is intended that both alternatives implement the reduction gear unit by means of a first and a second reduction-gear-unit gear wheel pair.

According to a first alternative, in a first shifted state of the reduction gear unit the main input shaft is coupled directly to the auxiliary input shaft, and in a second shifted state of the reduction gear unit the main input shaft is connected to the auxiliary input shaft via the first and second reduction-gear-unit gear wheel pair. Therefore, in the first shifted state there is no step-up or step-down transmission that occurs via the two gear wheel pairs but rather the main input shaft and the auxiliary input shaft are directly connected to one another via a clutch. The two reduction-gear-unit gear wheel pairs are correspondingly not in engagement with one another. Insofar as there is a change into the second shifted state, a “doubled” step-up or step-down transmission occurs via the two reduction-gear-unit gear wheel pairs. In the case of a step-up transmission, the first shifted state constitutes the high load state Hi, and the second shifted state constitutes the low load state Lo. Accordingly, in the case of a step-up transmission the first shifted state is the low load state Lo, and the second shifted state is the high load state Hi.

Such an embodiment is usually also referred to as a three-shaft arrangement, since the main input shaft and the auxiliary input shaft are arranged coaxially one next to the other, so that a direct coupling is easily possible. Both the main input shaft and the auxiliary input shaft have the same direction of rotation here independently of the shifted state. Therefore, a reversal of the direction of rotation occurs, on the one hand, between the input shaft unit and the auxiliary shaft and, on the other hand, between the auxiliary shaft and the output shaft. Correspondingly, the input shaft unit and the output shaft have the same direction of rotation.

According to a second embodiment, the direction of rotation of the output shaft can be reversed in comparison with the direction of rotation of the main input shaft. This takes place in that in a first shifted state of the reduction gear unit the main input shaft is connected to the auxiliary input shaft via the first reduction-gear-unit gear wheel pair and in a second shifted state of the reduction gear unit the main input shaft is connected to the auxiliary input shaft via the second reduction-gear-unit gear wheel pair. Correspondingly, a reversal of the direction of rotation therefore takes place between the main input shaft and the auxiliary input shaft. Such an embodiment is therefore also referred to as a four-shaft arrangement. One of the reduction-gear-unit gear wheel pairs here has a stepped-up transmission and the other reduction-gear-unit gear wheel pair has a stepped-down transmission. However, it is also possible for a reduction-gear-unit gear wheel pair to be embodied in such a way that neither a step-up nor a step-down transmission occurs so that merely the direction of rotation is reversed.

As explained above, each gear wheel pair of the front-mounted range unit and of the rear-mounted range unit has its own clutch. There are also two additional clutches for the reduction gear unit. The actuation of these clutches occurs via a hydraulic actuation arrangement. A further advantage of this disclosure is that the hydraulic actuation arrangement is always identical irrespective of the number of gear wheel pairs or of the gearshift variants, so that even in the case of subsequent adaptation there is no need to change the hydraulic actuation arrangement. The clutches of the front-mounted range unit and of the rear-mounted range unit are exclusively provided on the auxiliary input shaft and the output shaft, so that the auxiliary shaft is free of clutches. As a result, the individual shafts can be brought as close to one another as possible.

However, it also lies within the scope of the disclosure that clutches of the front-mounted range unit are arranged both on the auxiliary input shaft and on the auxiliary shaft. Correspondingly, the clutches of the rear-mounted range unit can also be arranged both on the auxiliary shaft and on the output shaft.

Thus, a multiplicity of different gearshift variants can be implemented, wherein the front-mounted range unit or the rear-mounted range unit have four gear wheel pairs.

The subject matter of the disclosure is also a method for running through a powershift transmission. Here, the reduction gear unit defines a first shift level, the front-mounted range unit defines a second shift level and the rear-mounted range unit defines a third shift level, wherein each shift level has at least two shifted states, and wherein the second shift level is arranged downstream with respect to the first shift level, and the third shift level is arranged downstream with respect to the second shift level.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned aspects of the present disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of the embodiments of the disclosure, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a schematic illustration of an agricultural working machine,

FIG. 2 shows a powershift transmission according to the disclosure with 32 gearshift variants,

FIG. 3 shows an alternative embodiment of the powershift transmission according to FIG. 2, and

FIG. 4 shows a shifting principle of the powershift transmission according to the disclosure.

Corresponding reference numerals are used to indicate corresponding parts throughout the several views.

DETAILED DESCRIPTION

The embodiments of the present disclosure described below are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present disclosure.

FIG. 1 shows an agricultural working machine in the form of a tractor 10 and any desired implement 12 which is towed by the tractor 10 and is embodied as a round bale press in the embodiment purely by way of example. The implement 12 comprises a chassis 14 which is supported on wheels 16 and has a bale-forming chamber 18. The implement 12 is towed by the tractor 10 by a drawbar 20. The driveable elements of the drawbar 20 are driven by the tractor 10 by a power take-off shaft 22.

The tractor 10 comprises a chassis 24 which is supported on front, steerable wheels 26 and driven wheels 28 at the rear. An operator workstation with a seat 32 is located in a cab 30. A steering wheel 34, an accelerator pedal 36 and an operator position 38 can be activated from the seat.

FIG. 2 shows a schematic diagram of the powershift transmission according to the disclosure. The powershift transmission has an input shaft unit composed of a main input shaft 41, an auxiliary input shaft 42 and an output shaft 61. An auxiliary shaft 51 is arranged with a parallel offset between the input shaft unit and the output shaft 61. A working machine 49, which transmits a torque to the main input shaft 41, is provided on the main input shaft 41. This torque is transmitted by the main input shaft 41 to the auxiliary input shaft 42 via a reduction gear unit 40, wherein a torque transmission between the auxiliary input shaft 42 and the auxiliary shaft 51 occurs via the front-mounted range unit 50. A torque transmission then occurs from the auxiliary shaft 51 to the output shaft 61 via a rear-mounted range unit 60.

In the illustrated embodiment which is shown by way of example, the front-mounted range unit 50 has a total of four gear wheel pairs I, II, III and IV, each composed of a drive gear wheel 52 and an output gear wheel 53, which can be engaged with one another via a clutch 54. These four gear wheel pairs I, II, III and IV are distinguished by different transmission ratios. For example, the gear wheel pair I has a relatively small drive gear wheel 52 and a large output gear wheel 53. As long as these gear wheels are in engagement with one another, the rotational speed of the output gear wheel 53 is reduced and at the same time the torque is increased. In comparison with this, the gear wheel pair IV has a relatively large drive gear wheel 52 and a relatively small output gear wheel 53, as a result of which the rotational speed of the output gear wheel 53 is increased and the torque is reduced.

In order to transmit the torque from the input shaft unit to the auxiliary shaft 51, the drive gear wheels 52 of the front-mounted range unit 50 are arranged on the auxiliary input shaft 52, and the output gear wheels 53 are arranged on the auxiliary shaft 51. The clutches of the front-mounted range unit 50 are exclusively arranged on the auxiliary input shaft 42, wherein it, of course, also lies within the scope of the disclosure to provide clutches 54 both on the auxiliary input shaft 42 and on the auxiliary shaft 51. In the case of an exclusive arrangement on the auxiliary input shaft 42, these clutches are arranged in a so-called back-to-back arrangement, wherein two of the clutches 54 are located between two of the gear wheel pairs I, II, III and IV of the front-mounted range unit 50.

Arranged between the main input shaft 41 and the auxiliary input shaft 42 is a reduction gear unit 40, via which the main input shaft 41 is connected to the auxiliary input shaft 42. The reduction gear unit 40 has a clutch Hi, via which the main input shaft 41 can be directly coupled to the auxiliary input shaft 42. For this purpose, the two input shafts 41, 42 are arranged one next to the other and coaxially with respect to one another, wherein the clutch Hi permits direct transmission of the torque, so that both the transmitted torque and the rotational speed remain unchanged after engagement of the clutch. This type of a connection constitutes a first shifted state of the reduction gear unit 40, which state describes a high load state.

In a second shifted state of the reduction gear unit 40, the main input shaft 41 is connected to the auxiliary input shaft 42 via a first and a second reduction-gear-unit gear wheel pair 43, 44. There, the output gear wheel of the first reduction-gear-unit gear wheel pair 43 can be coupled to the drive gear wheel of the second reduction-gear-unit gear wheel pair 44 via a clutch Lo. The drive gear wheel of the first reduction-gear-unit gear wheel pair 43 is arranged here on the main input shaft 41, and the output gear wheel of the second reduction-gear-unit gear wheel pair 44 is arranged on the auxiliary input shaft 42. Both reduction-gear-unit gear wheel pairs 43, 44 are embodied here in such a way that a transmission of a reduction of the rotational speed and the increase in the torque takes place. The second shifted state defines a low load state.

Irrespective of the shifted state of the reduction gear unit 40, the input shafts 41, 42 always have the same direction of rotation, which is reversed in comparison with the output shaft 61.

The transmission of the torque from the auxiliary shaft 51 to the output shaft 61 takes place via a rear-mounted range unit 60. For this purpose, the drive gear wheels 62 are arranged on the auxiliary shaft 51, and the output gear wheels 63 are arranged on the output shaft 61.

The rear-mounted range unit 60 also has four gear wheel pairs A, B, C and D. The number of gearshift variants results now from a multiplication of the gear wheel pairs of the front-mounted range unit 50, of the rear-mounted range unit 60 and the shifted states of the reduction gear unit 40. Therefore, a total of 32 gears can be implemented. Removing, for example, the gear wheel pair IV and the gear wheel pair D causes the number of gearshift variants to be reduced to only 18.

The individual gear wheel pairs A, B, C and D of the rear-mounted range unit 60 can also be coupled and decoupled via respectively assigned clutches 64, wherein in the example shown all the clutches 64 are arranged on the output shaft 61. The auxiliary shaft 51 is therefore free of clutches 54, 64. The arrangement of the clutches 64 corresponds, as in the arrangement of the clutches 54 already explained above, to the front-mounted range unit on the auxiliary input shaft.

Moreover, the powershift transmission has a reversing unit 70 which is integrated into the reduction gear unit 40.

FIG. 3 shows an alternative embodiment of the powershift transmission according to FIG. 2, which differs in the embodiment of the reduction gear unit 40. In contrast to FIG. 2, the main input shaft 51 and the auxiliary input shaft 52 cannot be coupled directly to one another. Instead, a first shifted state is implemented by means of the first reduction-gear-unit gear wheel pair 43, and a second shifted state is implemented by means of the second reduction-gear-unit gear wheel pair 44. The first reduction-gear-unit gear wheel pair 43 can be coupled in here by means of the clutch Lo and defines a low load state, while the second reduction-gear-unit gear wheel pair 44 is coupled by means of the clutch Hi and defines a high load state. The other components are embodied in a way analogous to the powershift transmission according to FIG. 2. In particular, the front-mounted range unit 50 also has four gear wheel pairs I, II, III and IV here, or else the rear-mounted range unit 60 has four gear wheel pairs A, B, C and D.

The essential difference with respect to the powershift transmission according to FIG. 2 is that a reversal of the direction of rotation takes place between the main input shaft 41 and the auxiliary input shaft 42. Overall, a reversal of the direction of rotation therefore takes place via the front-mounted range unit 50, via the reduction gear unit 40 and via the rear-mounted range unit 60, so that the output shaft 61 has a direction of rotation which is reversed in comparison with the main input shaft 41. In one embodiment according to FIG. 2, the main input shaft 41 and the output shaft 61 have the same direction of rotation.

FIG. 4 shows a shift principle of the powershift transmission. It is shown how the powershift transmission is to run through, in order to be able to change over as continuously as possible from a low gearshift variant into a high gearshift variant. In this context, the reduction gear unit 40 forms a first shift level, the front-mounted range unit 50 forms a second shift level, and the rear-mounted range unit 60 forms a third shift level.

At first, the front-mounted range unit 50 is shifted onto the gear wheel pair I, the reduction gear unit 40 is shifted into the shifted state Lo, and the rear-mounted range unit 60 is shifted onto the gear wheel pair A. In order to increase the gear, the reduction gear unit 40 is now placed firstly in the shifted state Hi, while both the front-mounted range unit 50 and the rear-mounted range unit 60 remain unchanged. In order to bring about a further increase, this is then repeated in particular in the case of a successively shifted increase in the front-mounted range unit 50, until all the gear wheel pairs I, II, III and IV of the front-mounted range unit 50 have been run through.

In a further step, the gear wheel pairs A, B, C and D of the rear-mounted range unit 60 are shifted through successively, wherein the shifting principle explained above is repeated for each gear wheel pair A, B, C and D of the rear-mounted range unit 60.

While embodiments incorporating the principles of the present disclosure have been disclosed hereinabove, the present disclosure is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims. 

1. A powershift transmission for an agricultural machine, comprising: a transmission housing, an input shaft unit and an output shaft, wherein the input shaft unit and the output shaft extend at least at a distance within the transmission housing, an auxiliary shaft arranged parallel to but offset between the input shaft unit and the output shaft, the auxiliary shaft being arranged within the transmission housing, wherein the input shaft unit and the auxiliary shaft are connected to one another via a front-mounted range unit, and the auxiliary shaft and the output shaft are connected to one another via a rear-mounted range unit, wherein the front-mounted and rear mounted range units each comprises at least two gear wheel pairs, the at least two gear wheel pairs being individually coupled or decoupled, further wherein the input shaft unit is formed from a main input shaft and an auxiliary input shaft.
 2. The powershift transmission of claim 1, wherein the main input shaft and the auxiliary input shaft are coupled to one another via a reduction gear unit.
 3. The powershift transmission of claim 1, wherein the reduction gear unit comprises a first and a second reduction-gear-unit gear wheel pair.
 4. The powershift transmission of claim 3, wherein the main input shaft is adapted to be coupled to a drive unit; wherein, in a first shifted state of the reduction gear unit, the main input shaft is coupled directly to the auxiliary input shaft, and in a second shifted state of the reduction gear unit the main input shaft is connected to the auxiliary input shaft via the first and the second reduction-gear-unit gear wheel pair.
 5. The powershift transmission of claim 3, wherein the main input shaft is adapted to be coupled to a drive unit such that in a first shifted state of the reduction gear unit, the main input shaft is connected to the auxiliary input shaft via the first reduction-gear-unit gear wheel pair, and in a second shifted state of the reduction gear unit the main input shaft is connected to the auxiliary input shaft via the second reduction-gear-unit gear wheel pair.
 6. The powershift transmission of claim 1, further comprising: drive gear wheels of the front-mounted range unit are arranged on the auxiliary input shaft; and output gear wheels of the front-mounted range unit are arranged on the auxiliary shaft.
 7. The powershift transmission of claim 1, further comprising: drive gear wheels of the rear-mounted range unit are arranged on the auxiliary shaft; and output gear wheels of the rear-mounted range unit are arranged on the output shaft.
 8. The powershift transmission of claim 1, wherein each gear wheel pair of the front-mounted range unit and of the rear-mounted range unit comprises a separately assigned clutch.
 9. The powershift transmission of claim 8, wherein the clutches of the front-mounted range unit and of the rear-mounted range unit are arranged on the auxiliary input shaft and the output shaft.
 10. The powershift transmission of claim 9, wherein the auxiliary shaft is free of clutches.
 11. The powershift transmission of claim 1, wherein a rotational direction of the output shaft is reversible via a reversing unit, the reversing unit integrated into the reduction gear unit.
 12. The powershift transmission of claim 1, wherein the front-mounted range unit or the rear-mounted range unit comprises four gear wheel pairs.
 13. A method for operating through a powershift transmission, comprising: providing a transmission housing, an input shaft unit, an output shaft, an auxiliary shaft arranged parallel to but offset between the input shaft unit and the output shaft; connecting the input shaft unit and the auxiliary shaft via a front-mounted range unit having at least two gear wheel pairs; connecting the auxiliary shaft and the output shaft via a rear-mounted range unit having at least two gear wheel pairs; forming the input shaft unit from a main input shaft and an auxiliary input shaft; defining a first shift level with a reduction gear unit; defining a second shift level via the front-mounted range unit; defining a third shift level via the rear-mounted range unit; arranging the second shift level downstream with respect to the first shift level; and arranging the third shift level downstream with respect to the second shift level; wherein each shift level comprises at least two shifted states.
 14. A powershift transmission for an agricultural machine, comprising: a transmission housing; an input shaft unit; an output shaft, wherein the input shaft unit and the output shaft extend at least at a distance within the transmission housing; a main input shaft and an auxiliary input shaft, the main input shaft and the auxiliary input shaft forming the input shaft unit; an auxiliary shaft arranged parallel to but offset between the input shaft unit and the output shaft, the auxiliary shaft being arranged within the transmission housing; a front-mounted range unit for connecting the input shaft unit and the auxiliary shaft; a rear-mounted range unit for connecting the auxiliary shaft and the output shaft; a reduction gear unit for coupling the main input shaft and the auxiliary input shaft; wherein the front-mounted and rear mounted range units each comprises at least four gear wheel pairs, the at least four gear wheel pairs being individually coupled or decoupled.
 15. The powershift transmission of claim 14, wherein each gear wheel pair of the front-mounted range unit and of the rear-mounted range unit comprises a separately assigned clutch.
 16. The powershift transmission of claim 15, wherein the clutches of the front-mounted range unit and of the rear-mounted range unit are arranged on the auxiliary input shaft and the output shaft.
 17. The powershift transmission of claim 16, wherein the auxiliary shaft is free of clutches.
 18. The powershift transmission of claim 14, wherein a rotational direction of the output shaft is reversible via a reversing unit, the reversing unit integrated into the reduction gear unit.
 19. The powershift transmission of claim 14, wherein the main input shaft is adapted to be coupled to a drive unit; wherein, in a first shifted state of the reduction gear unit, the main input shaft is coupled directly to the auxiliary input shaft, and in a second shifted state of the reduction gear unit the main input shaft is connected to the auxiliary input shaft via a first and a second reduction-gear-unit gear wheel pair.
 20. The powershift transmission of claim 14, wherein the main input shaft is adapted to be coupled to a drive unit such that in a first shifted state of the reduction gear unit, the main input shaft is connected to the auxiliary input shaft via a first reduction-gear-unit gear wheel pair, and in a second shifted state of the reduction gear unit the main input shaft is connected to the auxiliary input shaft via a second reduction-gear-unit gear wheel pair. 